Controlled Release Structure for Attaching Medical Devices

ABSTRACT

A medical device for use with a fluid transfer device includes a hub having an open proximal end with a frusto-conically-shaped cavity therein, a distal end and a passageway therethrough. The cavity is part of the passageway. A release element in the passageway of the hub is positioned to block fluid-tight engagement of the frusto-conically-shaped tip with the cavity of the hub. Structure is provided to release at least part of the release element, upon application of a proximally directed force on the hub, to allow the abrupt fluid-tight engagement of the tip and the cavity in the hub.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/619,658 filed Jan. 4, 2007 which is a continuation of U.S. patentapplication Ser. No. 10/428,720 filed May 2, 2003 which has been issuedas U.S. Pat. No. 7,217,258, all of which are incorporated herein byreference in their entireties.

FIELD OF THE INVENTION

The present invention relates to a medical device such as a hypodermicneedle assembly which is adapted to releasably engage a fluid transferdevice such as a syringe. In particular, the present invention relatesto a medical device having a releasable element for controlling theminimum force needed to connect a medical device to a fluid deliverydevice such as a needle assembly and a syringe.

BACKGROUND

A hypodermic syringe consists of a cylindrical barrel, most commonlymade of thermoplastic material or glass, with a distal end adapted to beconnected to a hypodermic needle assembly or other medical device and aproximal end adapted to receive a stopper and plunger rod assembly. Thestopper provides fluid-tight seal between itself and the syringe barrelso that movement of the stopper up and down the barrel will causeliquid, blood or other fluids to be drawn into or forced out of thesyringe barrel through the distal end. The stopper is moved along thesyringe barrel by applying axial force on a rigid plunger rod which isconnected to the stopper and is sufficiently long to be accessibleoutside of the barrel. The stopper and the plunger rod can be integrallyformed of one material such as thermoplastic.

Hypodermic needle assemblies, typically including a cannula and a hub,are often removably attached to syringes for performing a variety oftasks such as the delivery of medication into patients and into devices,and for withdrawing fluid samples from patients and from fluid sources.Usually, the hub of the hypodermic needle assembly has tapered interiorsurface adapted to engage the tapered tip of the syringe barrel so thatthe two components are joined in a frictional interference fit. Thetapered syringe tip and the complementarily tapered receptacle in thehub are referred to as standard luer fittings. A wide variety of othermedical devices such as stopcocks and tubing sets have standard luerfittings which allow them to be engaged to a syringe tip.

It is important that the frictional fit between the syringe tip and theneedle hub or other medical device is strong enough to preventaccidental disengagement caused by the fluid pressures within thesyringe and/or other factors such as forces applied to the needle hubwhen actuating safety needle shields connected to the hub. If thesyringe tip becomes disengaged from the needle assembly, medication,blood or other fluids will be lost, and there is also potential forcontamination.

The prior art teaches many structures for improving the connectionbetween medical devices having tapered luer fittings such as needleassemblies and syringes. These structures include complementary engagingstructure on both the needle hub and syringe barrel tip such asprojections and recesses providing for a snap-fit arrangement. Manuallyreleasable locking structures have been provided to increase theconnection between the needle hub and barrel tip while allowingreasonable forces for disconnection of these components. Also,enhancements to the luer tip of the syringe barrel such as coatings,sandblasting and mechanical collars have provided for improvedconnection between a needle hub and a syringe barrel tip. Many of thestructures taught by the prior art do not contemplate the subsequentremoval of the needle assembly from the syringe barrel. Others requireextensively modified needle hubs and barrel tips. Structures having atapered luer fitting such as a needle assembly and syringe barrel areadequate for normal use when the needle assembly is properly installedon the syringe tip. Difficulties can arise if the user does not useenough force to frictionally engage the luer tapered surfaces which canresult in inadvertent disconnection of the needle assembly.

Although the prior art teaches various devices and structures forimproving the strength of the connection between a syringe barrel andthe hub of a needle assembly or other fluid handling device, there isstill a need for a simple, straight-forward, reliable needle hub orother fluid-handling device having structure which improves the strengthof the connection with the syringe tip or other device having a standardtapered luer tip by requiring a minimum force of engagement.

SUMMARY OF THE INVENTION

A medical device for use with a fluid transfer device having afrusto-conically shaped tip includes a hub having an open proximal endwith a frusto-conically-shaped cavity therein, a distal end and apassageway therethrough. The cavity is part of the passageway. A releaseelement is positioned in the passageway of the hub to block fluid-tightengagement of the frusto-conically shaped tip with the cavity of thehub. Structure is provided for releasing at least part of the releaseelement, upon application of a proximally directed force on the hub, toallow the abrupt fluid-tight engagement of the tip and the cavity in thehub. The abrupt transition to fluid-tight engagement can provide atactile and audible indication to the user that the hub and the tip areproperly engaged.

The medical device of the present invention may also include a needlecannula having an open proximal end, a distal end and a lumentherethrough. The proximal end of the needle cannula is joined to thedistal end of the hub so that the lumen is in fluid communication withthe passageway in the hub.

The proximally directed force on the hub is desirably greater than 0.5kg. and preferably between 1 kg. and 5 kg.

The structure for allowing the release of part of the release elementmay include a discontinuity on the release element or the hub engaging acomplementary discontinuity on the hub or the release element. Thediscontinuities are configured to disengage upon the application of theproximally directed force on the hub. The hub may include a proximallydirected hollow extension in the passageway having a discontinuitythereon and configured to allow fluid flow through the passageway. Therelease element includes a complementary discontinuity thereon engagesthe discontinuity and is positioned so that upon disengagement inresponse to the proximally-directed force, at least part of the releaseelement moves distally into the space around the extension. The releaseelement is configured to allow fluid flow through the passageway.

An alternative release element includes a proximal end and a distal endcapable of telescoping action with respect to each other. The structurefor releasing includes at least one frangible link between the proximaland distal end of the release element. The link is breakable uponapplication of the proximally-directed force on the hub so that theproximal and distal ends of the release element can telescope withrespect to each other and allow engagement of the tip and the hub.Adhesive may be used as a frangible structure to allow the release ofpart or all of the release element in various embodiments.

Another alternative release element includes a distal end positioned inthe passageway in the hub and a proximal end including a proximallydirected axial beam. The beam has a free end adapted to contact thedistal end of the frusto-conically-shaped tip to block fluid-tightengagement of the tip and the hub. The beam is configured to buckle uponapplication of the proximally directed force on the hub.

Another alternative embodiment of the needle assembly of the presentinvention further includes a guide element on the hub having an aperturetherethrough. An elongate barrier arm having a proximal end and a distalend is positioned in the aperture for sliding axial movement therein.The distal end of the barrier arm includes a barrier element having adistal end, a proximal end and a needle passageway therethrough. Theneedle cannula is positioned at least partially within the needlepassageway of the barrier element. The barrier arm is movable from atleast a first retracted position wherein the distal end of the needlecannula passes completely through the barrier element so that the distalend of the needle cannula is exposed, to a second extended positionwherein the barrier element surrounds the distal end of the needlecannula to prevent incidental contact with the distal end of the needlecannula. A finger contact surface on the barrier arm is provided toaccept digital force to the barrier arm to move the barrier arm into thesecond extended position.

Still another alternative embodiment of the needle assembly of thepresent invention further includes a needle guard having a proximal end,a distal end and a needle passageway therethrough. The needle guard ismovable along the needle cannula from a first position substantiallyadjacent the proximal end of the needle cannula to a second positionwhere a distal tip of the needle cannula is intermediate the opposedproximal and distal ends of the needle guard. A hinged arm havingproximal and distal segments articulated to one another for movementbetween a first position wherein the segments are substantiallycollapsed onto one another and a second position where the segments areextended from one another is provided. The proximal segment of thehinged arm is articulated to a portion of the hub. The distal segment ofthe hinged arm is articulated to the needle guard. The proximal anddistal segments of the hinged arm have respective lengths for permittingthe guard to move from the first position to the second position on theneedle cannula and for preventing the guard from moving distally beyondthe second position. The components of the hinged arm may be integrallymolded of thermoplastic material.

All embodiments of the present invention may include a needle cannulaand a pivotable needle shield having a cavity therein hingedly connectedto the hub and capable of pivoting from a needle exposing position,which allows access to the distal end of the needle cannula, and aneedle protecting position wherein the distal end of the needle cannulais within the cavity of the needle shield.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective exploded view illustrating a needle assembly ofthe present invention and a syringe barrel.

FIG. 2 is a perspective view of the needle assembly of FIG. 1 connectedto the syringe barrel.

FIG. 3 is an enlarged partial cross-sectional view of the needleassembly and syringe barrel of FIG. 1 taken along line 3-3.

FIG. 4 is a perspective view of the release element of the needleassembly.

FIG. 5 is an enlarged partial cross-sectional view of the needleassembly and syringe barrel illustrating the position of the releaseelement before hub and barrel tip engagement.

FIG. 6 is a perspective partial cross-sectional view of the needleassembly and the syringe barrel tip similar to FIG. 3.

FIG. 7 is a partial cross-sectional perspective view illustrating theneedle assembly frictionally engaged to a syringe barrel.

FIG. 8 is a perspective view of a syringe barrel and an alternativeneedle assembly having a rotatable needle shield.

FIG. 9 is an enlarged cross-sectional view of the syringe barrel andneedle assembly of FIG. 8 taken along line 9-9.

FIG. 10 is an alternative release element of the present invention.

FIG. 11 is a perspective cross-sectional view of the release element ofFIG. 10 taken along line 11-11.

FIG. 12 illustrates a needle assembly having the release element of FIG.10 and the syringe barrel before frictional engagement of the barrel tipand the hub.

FIG. 13 is a partial cross-section side elevation view of the needleassembly of FIG. 12 frictionally engaged to the syringe barrel tip.

FIG. 14 is a side-elevational view of an alternative embodiment of theneedle assembly of the present invention illustrated after frictionalengagement with a syringe barrel tip.

FIG. 15 is a cross-sectional view of the needle assembly and syringebarrel of FIG. 14 taken along line 15-15.

FIG. 16 is side-elevational view of another alternative embodiment ofthe needle assembly of the present invention illustrated afterfrictional engagement with a syringe barrel tip.

FIG. 17 is a cross-sectional view of the needle assembly and syringebarrel of FIG. 16 taken along line 17-17.

FIG. 18 is a partial cross-sectional view of another alternativeembodiment of the needle assembly of the present invention illustratedbefore frictional engagement with a syringe barrel tip.

FIGS. 19 and 20 illustrate the needle assembly of FIG. 18 afterfrictional engagement with a syringe barrel tip.

FIG. 21 is a perspective view of another alternative needle assembly ofthe present invention.

FIG. 22 is an enlarged cross-sectional view of the needle assembly ofFIG. 21 taken along line 21-21.

DETAILED DESCRIPTION

While this invention is satisfied by embodiments in many differentforms, there are shown in the drawings and will herein be described indetail, preferred embodiments of the invention with the understandingthat the present disclosure is to be considered exemplary of theprinciples of the invention and not intended to limit the invention tothe embodiments illustrated. The scope of the invention will be measuredby the appended claims and their equivalents.

Referring to FIGS. 1-7, a medical device such as needle assembly 20includes a needle cannula 21 having a proximal end 22, a distal end 23and a lumen 24 therethrough defining a longitudinal axis 25. A hub 31includes an open proximal end 32 with a cavity 33 therein, a distal end34 and a passageway 35 therethrough. The cavity is part of thepassageway. The proximal end of the needle cannula is joined to thedistal end of the hub so that the lumen of the needle cannula is influid communication with the passageway of the hub.

Needle cannula 21 is preferably made of metal such as stainless steeland can be held to the hub using various manufacturing methods withadhesives such as epoxy being preferred. The hub is preferably made ofinjection moldable plastic such as polypropylene, polyethylene,polycarbonate and combinations thereof. The needle cannula and hub maybe integrally formed of thermoplastic material. The needle assembly canbe used with a variety of fluid transfer devices having afrusto-conically shaped luer tip such as a hypodermic syringe.

A syringe includes syringe barrel 61 having a inside surface 62 defininga chamber 63, an open proximal end 64, and a distal end 65 including anelongate frusto-conically shaped tip 67 having a conduit 68therethrough. The needle assembly is connected to the syringe barrel sothat the frusto-conically shaped tip is in fluid-tight engagement withthe frusto-conically shaped cavity in the hub and the lumen is in fluidcommunication with the cavity. A concern with prior art needleassemblies and syringe barrels having complementary luer fittings isthat the needle assembly may become loosened or disengaged from thesyringe tip during use. This may happen because the user does not applyenough axial force to properly engage the needle hub to the barrel tip,and the hydraulic pressure of the injection process and/or forcesinduced during normal use dislodge the needle assembly from the barrel.

The present invention provides a medical device having a fluid transferfitting, such as a needle hub, which can be used with any standard luerslip fitting to provide improved retention of the needle assembly to theluer slip fitting and to allow for more uniform installation force aswill be explained in detail hereinafter. This improvement isaccomplished through the use of a release element such as releaseelement 45 in the passageway of the hub. Release element 45 ispositioned to block fluid-tight engagement of the frusto-conicallyshaped tip of the syringe barrel with the cavity of the hub. In thisembodiment the release element is positioned in a distal end 41 ofcavity 33. Means for releasing at least part of the release element,upon application of a proximally directed force on the hub, to allow theabrupt fluid-tight engagement of the tip and the cavity in the hub isprovided. In this embodiment, means for releasing includes adiscontinuity on the release element or the hub engaging a complementarydiscontinuity on the other of the release element or the hub.Discontinuities are configured to disengage upon the application of aproximally directed force on the hub. In this embodiment, the hubincludes a proximally directed hollow extension 37 in the passagewayhaving a discontinuity in the form of radial projection 38 thereon.Hollow extension 37 is configured to allow fluid flow through thepassageway and defines an annular space 39. Release element 45 containsa complementary discontinuity in the form of inwardly directed edge 46thereon. Radial projection 38 and inwardly directed edge 46 areconfigured to release when a pre-determined proximally-directed forceused to engage the cavity of the hub on the tip of the barrel isapplied. Specifically, the force between proximal end 47 of the releaseelement and a distal end 69 of tip 67 will cause radial projection 38 ofthe hub to disengage inwardly directed edge 46 of the release elementallowing the release element to move forward so that at least a portionof the release element is in annular space 39 of the hub. The relativelyabrupt release of the release element allows the cavity of the hub toengage the tip of the syringe barrel with sufficient force to provide anadequate frictional interference fit between an inside surface 40 ofcavity 33 and an outside surface 70 of tip 67, as best illustrated inFIG. 7. An important advantage of the present invention is that therelease element and the hub can be configured to provide an audibleclick when the hub engages the tip of the barrel and/or to maximize thetactile feeling when engagement occurs to give the user positivefeedback that the needle assembly is properly engaged to the syringebarrel tip.

An important advantage of the present invention is that it will notallow a frictional fluid-tight engagement between the tip of the syringebarrel and the cavity in the hub until a pre-determined force which canprovide a generally adequate frictional interference fit between the huband the syringe tip is reached. This feature eliminates the ability ofthe user to connect the hub to the syringe barrel using less than apredetermined force needed to provide a frictional interference fit thatwill usually be strong enough to maintain itself during normal use ofthe medical device. This important advantage can be achieved when usingthe present invention with standard luer slip tips on syringe barrelsand other fluid delivery devices without the need to modify the luertip.

The discontinuities and complementary discontinuities on the releaseelement and the hub can encompass a wide variety of structures includingprojections and recesses either singular or multiple to produce asnap-fit arrangement or overlapping dimensions to produce a press-fitrelationship between the release element and the hub and variationsthereof wherein the release element must overcome a physical engagementwith the hub to release therefrom. Means for releasing as used herein isintended to include the structures described above and other means suchas adhesives or frangible connections between the release element andthe hub which break or disconnect upon application of the desired force.Means for releasing may also include an additional element between therelease element and the hub. All these variations fall within thepurview of the present invention, and the interference or snap-fitrelationship of the retaining element to the hub illustrated in FIGS.1-7 is merely representative of these many possibilities.

The release element is made of sheet metal such as stainless steel butcan be fabricated in a wide variety of materials and configurations thatwill allow it to perform its function to release upon the application ofthe desired force. The desired force may vary based on the materialsused to construct the hub and the surface finish of the cavity. For mostapplications involving plastic tips on standard luer tip syringes andother fluid transfer devices, a proximally directed force of equal orgreater than 0.5 kg (1.1 pounds) is desired to cause the release of therelease element. A release under a proximally directed force of between1 kg and 5 kg (2.2 pounds and 11 pounds) is preferred.

In use, as best illustrated in FIGS. 3 and 5-7, needle assembly 20 isconnected to syringe barrel 61 by placing the elongate frusto-conicallyshaped barrel tip into the frusto-conically-shaped cavity of the needlehub until distal end 69 of tip 67 contacts proximal end 47 of releaseelement 45 and applying an axial force sufficient to release the releaseelement and allow the abrupt fluid-tight engagement of the tip and thecavity in the hub as illustrated in FIG. 7. During installation, all orpart of the release element moves distally in the hub cavity to allowengagement of the barrel tip and the hub cavity.

FIGS. 8-9 illustrate an alternative embodiment of the needle assembly ofthe present invention. In this embodiment, needle assembly 120 includesa needle cannula 121 having a proximal end 122, a distal end 123 and ahub 131. Hub 131 includes an open proximal end 132 with afrusto-conically shaped cavity 133, a distal end 134 and a passageway135 therethrough. The cavity is part of the passageway. The proximal endof the needle cannula is joined to the distal end of the hub so that thelumen of the needle cannula is in fluid communication with thepassageway. A release element 145 is in the passageway of the hubpositioned to block fluid-tight engagement of the frusto-conicallyshaped tip with the cavity of the hub until all or part of the releaseelement is displaced distally in the passageway by action of forceapplied to the release element by the distal end of the syringe barreltip as illustrated in FIG. 9. Release element 145 functions in a similarmanner as release element 45 in the embodiment of FIGS. 1-7. Hub 131further includes a pivotable needle shield 171 which is hingedlyconnected to the hub and capable of pivoting from a needle exposingposition, as illustrated in FIGS. 8-9, which allows access to the distalend of the needle cannula and a needle protecting position wherein thedistal end of the needle cannula is within cavity 172 of the needleshield. A structure used to provide the pivotable relationship betweenthe hub and the needle shield can include a variety of hinges, linkages,living hinges and the like. In this embodiment, axel 173 on the needleshield engages axel housing 174 on the hub to provide the pivotablerelationship.

After use, the user pivots the needle shield into the needle protectingposition by applying a digital force to the needle shield. Such a forcehas at least a component in direction A as illustrated in FIG. 8. Thepresent invention is especially useful as a hinged needle shield needleassembly. Force A is another force which may contribute to theunintentional disconnection of the needle assembly from the syringebarrel which is resisted by the frictional interference fit of aproperly installed hub.

FIGS. 10-12 illustrate an alternative embodiment of the medical deviceof the present invention. In this embodiment, a needle assembly 220includes a needle cannula 221 having a proximal end 222, a distal endand a lumen 224 therethrough. A hub 231 includes an open proximal end232 with a cavity 233 therein, a distal end 234 and a passageway 235therethrough. The cavity is part of the passageway. The proximal end ofthe needle cannula is joined to the distal end of the hub so that thelumen of the needle cannula is in fluid communication with thepassageway of the hub. Needle assembly 220 is illustrated with a syringebarrel 61 having a distal end 65 including an elongatefrusto-conically-shaped tip 57 having a conduit 58 therethrough. As withthe embodiment of FIGS. 1-7, the present embodiment includes a releaseelement 245 in the passageway of the hub, positioned to blockfluid-tight engagement of the frusto-conically-shaped tip with thecavity in the hub, as best illustrated in FIG. 12. Release element 245includes a proximal end 247 and a distal end 249 capable of telescopingaction with respect to each other. In this embodiment, means forreleasing includes at least one frangible link 250 between the proximalend and the distal end of the release element. The frangible link isbreakable upon application of a proximally-directed force on the hub sothat the proximal end distal ends of the release element can telescopewith respect to each other to allow engagement of the syringe barrel tipand the needle assembly hub as best illustrated in

FIG. 13. The proximal portion of the release element further includes adistally directed aligning projection 251 which extends into theinterior of the distal portion of the release element. The aligningprojection is intended to align and center the distal portion withrespect to the proximal portion, after frangible link 250 has broken, tohelp ensure smooth telescoping action between the two elements. Thereshould be at least one frangible link in the release element with aplurality of frangible links being preferred. It is also preferred thatthe distal end of the release element has an opening therein largeenough to accept at least part of the proximal end of the releaseelement when the frangible link is broken. The release element of thepresent embodiment preferably is cylindrically-shaped with one end ofthe release element having an outside diameter which is smaller than theinside diameter of the other end of the release element. The frangiblelink extends between the inside diameter and the outside diameter. Thefrangible link is preferably integrally formed with the proximal anddistal ends of the release element. Adhesives and thermoplasticelastomers may also be used to form a frangible link along with otherdisengageable structures between the proximal and distal portions all ofwhich are within the purview of the present invention. The integrallyformed frangible link illustrated is merely representative of one ofthese many possibilities, all of which are within the purview of thepresent invention.

FIGS. 14 and 15 illustrate another alternative embodiment of the medicaldevice of the present invention. In this embodiment, needle assembly 320includes a needle cannula 321 having a proximal end 322, a distal end323 and a lumen therethrough. A hub 331 includes an open proximal end332 with a frusto-conically-shaped cavity 333 therein, a distal end 334and a passageway therethrough. The cavity is part of the passageway. Theproximal end of the needle cannula is joined to the distal end of thehub so that the lumen is in fluid communication with the passageway. Arelease element 345 is in the passageway of the hub positioned to blockfluid-tight engagement of frusto-conically shaped tip 367 of syringebarrel 61 with the cavity of the hub until all or part of the releaseelement is displaced distally in the passageway by action of forceapplied to the release element by the distal end of the syringe barreltip as illustrated in FIG. 15. Release element 345 functions in asimilar manner as release element 245 in the embodiment of FIGS. 10-13.Hub 331 further includes a guide element 376 having an aperture 377therethrough. An elongate barrier arm 379 having a proximal end 380 anda distal end 381 includes a barrier element 382 on distal end 381. Thebarrier element includes a proximal end 383, a distal end 385 and aneedle passageway 386 therethrough. The barrier arm is positioned withinthe aperture of the guide element and the needle cannula is positionedat least partially within the needle passageway of the barrier element.The barrier element is movable from at least a first retracted position,illustrated in FIGS. 14-15, wherein the distal end of the needle cannulapasses completely through the barrier element so that the distal end ofthe needle cannula is exposed, to a second extended position (notillustrated) wherein the barrier element surrounds the distal end of theneedle cannula to prevent incidental contact with tip 326 on the distalend of the needle cannula. A finger contact surface 387 on the barrierarm is provided for applying digital force to the barrier arm to movethe barrier arm into the second extended position. This is accomplishedby applying a digital force to the finger contact surface having atleast a component in direction B as illustrated in FIG. 14. The aperturein the guide element can be any shape, closed or open, which workscooperatively to guide the barrier arm between the first retractedposition and the second extended position. The barrier arm may be curvedor the aperture in the guide element angled so that the needlepassageway misaligns with tip 326 on the needle cannula to help preventmovement of the barrier element from the second extended position.

FIGS. 16-17 illustrate another alternative embodiment of the needleassembly of the present invention. In this embodiment, needle assembly420 includes a needle cannula 421 having a proximal end 422, a distalend 423 and a hub 431. Hub 431 includes an open proximal end 432 with afrusto-conically shaped cavity 433, a distal end 434 and a passageway435 therethrough. The cavity is part of the passageway. The proximal endof the needle cannula is joined to the distal end of the hub so that thelumen of the needle cannula is in fluid communication with thepassageway. A release element 445 is in the passageway of the hubpositioned to block fluid-tight engagement of a frusto-conically shapedtip such as tip 67 on syringe barrel 61 with the cavity of the hub untilall or part of the release element is displaced distally in thepassageway by action of force applied to the release element by thedistal end of the syringe barrel tip as illustrated in FIG. 17. Releaseelement 445 functions in a similar manner to the release element 245 inFIGS. 10-13. Needle assembly 420 further includes a needle guard 488having a proximal end 489, a distal end 490 and a needle passageway 491therethrough. The needle guard is movable along the needle cannula froma first position substantially adjacent to the proximal end of theneedle cannula, as illustrated in FIGS. 16-17, to a second positionwhere a distal tip 426 of needle cannula is intermediate the opposedproximal and distal ends of needle guard 488. A hinged arm 492 having aproximal segment 493 and a distal segment 494 which are articulated toone another for movement between a first position where the segments aresubstantially collapsed onto one another, as illustrated in FIGS. 16-17,and a second position where the segments are extended from one another.The proximal segment of the hinged arm is articulated to a portion ofthe hub through a structure that allows such movement, such as hinge 495in this embodiment. The distal segment of the hinged arm is articulatedto needle guard 488 through hinge 496. Proximal segment 493 and distalsegment 494 are articulated with respect to each other through hinge497. The proximal and distal segments of the hinged arm have respectivelengths for permitting the needle guard to move from the first positionto the second position on the needle cannula and for preventing theguard from moving distally beyond the second position. The needle guardis moved to the second position through the application of a digitalforce having at least a component in direction C as illustrated in FIG.17. The hinges may be mechanical hinges or linkages or flexibleconnections such as living hinges.

FIGS. 18-20 illustrate another alternative embodiment of the medicaldevice of the present invention. In this embodiment, needle assembly 520includes a needle cannula 521 having a proximal end 522, a distal endand a lumen therethrough. A hub 531 includes an open proximal end 532with a frusto-conically shaped cavity 533 therein, a distal end 534 anda passageway 535 therethrough. The cavity is part of the passageway. Theproximal end of the needle cannula is joined to the distal end of thehub so that the lumen is in fluid communication with the passageway. Arelease element 545, in the passageway, is positioned to blockfluid-tight engagement of frusto-conically shaped tip 567 of syringebarrel 61 with cavity 533 of hub 531. In this embodiment, releaseelement 545 includes distal end 549 positioned in the passageway andproximal end 547 which includes proximally directed axial beam 552. Theaxial beam includes a free end 553 adapted to contact distal end 69 ofthe barrel tip to block fluid-tight engagement of the tip and the hub.In this embodiment means for releasing includes the axial beam beingconfigured to buckle upon application of a pre-determinedproximally-directed force as best illustrated in FIGS. 19 and 20. Axialbeam 552 preferably has a rectangularly-shaped cross section. The distalend of the release element also includes at least one channel andpreferably a plurality of channels 545 for accepting liquid flow from asyringe barrel through the passageway. A wide variety of materials canbe used to produce a buckling beam with thermoplastic being preferred.It is also preferred that the entire release element 545 be integrallyformed of the same material, preferably thermoplastic. Also, it isdesirable to have the release element and the hub integrally formed ofthe same material, preferably thermoplastic.

FIGS. 21 and 22 illustrate another embodiment of the needle assembly ofthe present invention. In this embodiment, needle assembly 620 includesa needle 621 having a proximal end 622, a distal end 623 and a hub 631.Hub 631 includes an open proximal end 632 with a frusto-conically shapedcavity 633, a distal end 634 and a passageway 635 therethrough. Thecavity is part of the passageway. The proximal end of the needle isjointed to the distal end of the hub so that the needle projectsdistally outwardly from the distal end of the hub. A release element 645is in the passageway of the hub positioned to block fluid-tightengagement of the frusto-conically shaped tip of a medical device suchas a syringe barrel with the cavity of the hub until all or part of therelease element is displaced distally in the passageway by action offorce applied to the release element by the distal end of the syringebarrel tip. Release element 645 functions in a similar manner as releaseelement 45 in the embodiment of FIGS. 1-7. Needle 621 does not have afunctioning lumen and in this embodiment has a bifurcated distal tip626. Solid needles such as the needle having a bifurcated tip arecommonly used for administering vaccines, antigens and other substancesto the skin. The bifurcated tip is used to scratch or slightly piercethe skin of the patient so that the liquid substance, such as a vaccine,may be absorbed into the skin of the patient. The needle assembly ofthis embodiment can be attached to a syringe barrel, wherein the syringebarrel is used as a handle to control and guide the needle tip duringthe vaccination process.

What is claimed is:
 1. A medical device for use with a fluid transfer device having a frusto-conically shaped tip comprising: a hub having an open proximal end with a frusto-conically shaped cavity therein, a distal end and a passageway therethrough, said cavity being part of said passageway; and a release element in said passageway of said hub positioned to block fluid-tight engagement of said frusto-conically shaped tip with said cavity of said hub, said release element including a distal end in said passageway and a proximal end including a proximally directed axial beam, said beam having a free end adapted to contact the distal end of said frusto-conically shaped tip to block fluid-tight engagement of said tip and said hub; wherein said beam buckles upon application of a proximally directed force on said hub, to allow the abrupt fluid-tight engagement of said tip and said cavity in said hub.
 2. The medical device of claim 1 wherein said beam has a rectangularly shaped cross-section.
 3. The medical device of claim 1 wherein said distal end of said release element includes at least one channel for accepting liquid flow from said fluid delivery device through said passageway.
 4. The medical device of claim 1 wherein said at least one channel is a plurality of channels.
 5. The needle assembly of claim 1 wherein said release element is made of thermoplastic material
 6. The needle assembly of claim 1 wherein said release element and said hub are integrally formed of thermoplastic material.
 7. The medical device of claim 1 wherein said hub is made of thermoplastic material.
 8. The medical device of claim 7 wherein said thermoplastic material consists of materials selected from the group of polypropylene, polyethylene, polycarbonate and combinations thereof
 9. The medical device of claim 1 further including a needle cannula having a proximal end, a distal end and a lumen therethrough, said proximal end of said needle cannula being joined to said distal end of said hub so that said lumen is in fluid communication with said passageway.
 10. The medical device of claim 1 further including an elongate needle having a proximal end and a distal end, said proximal end of said needle being joined to said distal end of said hub.
 11. The medical device of claim 9 wherein said hub includes a pivotable needle shield having a cavity therein hingedly connected to said hub and capable of pivoting from a needle exposing position which allows access to said distal end of said needle cannula and a needle protecting position wherein said distal end of said needle cannula is within the cavity of said needle shield.
 12. The medical device of claim 9 further comprising: a guide element on said hub having an aperture therethrough; an elongate barrier arm having a proximal end and a distal end, said distal end of said barrier arm including a barrier element having a distal end, a proximal end and a needle passageway therethrough, said barrier arm positioned within said aperture of said guide element and said needle cannula positioned at least partially within said needle passageway of said barrier element, said barrier arm being movable from at least a first retracted position wherein said distal end of said needle cannula passes completely through said barrier element so that said distal end of said needle cannula is exposed, to a second extended position wherein said barrier element surrounds said distal end of said cannula to prevent incidental contact with said distal end of said needle cannula; and finger contact surface on said barrier arm for applying digital force to said barrier arm to move said barrier arm into said second extended position.
 13. The medical device of claim 9 further comprising: a needle guard having a proximal end, a distal end and a needle passageway therethrough, said needle guard being movable along said needle cannula from a first position substantially adjacent said proximal end of said needle cannula to a second position where distal tip of said distal end of said needle cannula is intermediate said opposed proximal and distal ends of said needle guard; a hinged arm having proximal and distal segments articulated to one another for movement between a first position where said segments are substantially collapsed onto one another and a second position where said segments are extended from one another, said proximal segment of said hinged arm being articulated to a portion of said hub, said distal segment of said hinged arm being articulated to said guard, said proximal and distal segments of said hinged arm having respective lengths for permitting said guard to move from said first position to said second position on said needle cannula, and for preventing said guard from moving distally beyond said second position.
 14. The medical device of claim 13 wherein said needle guard, said proximal segment and said distal segment are integrally formed of thermoplastic material.
 15. The medical device of claim 1 further including a syringe barrel having an inside surface defining a chamber, an open proximal end and a distal end including an elongate frusto-conically shaped tip having a conduit therethrough, said medical device being connected to said syringe barrel so that said frusto-conically shaped tip is in fluid-tight engagement with said frusto-conically shaped cavity of said hub and said passageway is in fluid communication with said chamber.
 16. The medical device of claim 1 wherein said proximally directed force is equal or greater than 0.5 kg. (1.1 pounds).
 17. The medical device of claim 1 wherein said proximally directed force is between 1 kg. and 5 kg.(2.2 pounds and 11 pounds).
 18. The medical device of claim 1 wherein the hub and the release element are configured to provide an audible indication of said abrupt fluid-tight engagement of said tip and said cavity.
 19. A medical device for use with a fluid transfer device having a frusto-conically-shaped tip comprising: a needle cannula having a proximal end, a distal end and a lumen therethrough; a hub having an open proximal end with a frusto-conically shaped cavity therein, a distal end and a passageway therethrough, said cavity being part of said passageway, said proximal end of said needle cannula being joined to said distal end of said hub so that said lumen is in fluid communication with said passageway; a release element in said passageway of said hub positioned to block fluid-tight engagement of said frusto-conically shaped tip with said cavity of said hub, said release element including a distal end in said passageway and a proximal end including a proximally directed axial beam, said beam having a free end adapted to contact the distal end of said frusto-conically shaped tip to block fluid-tight engagement of said tip and said hub; wherein said beam buckles upon application of a proximally directed force or equal or greater than 0.5 kg (1.1 pounds) on said hub, to allow the abrupt fluid-tight engagement of said tip and said cavity in said hub. 